[Python-Dev] setuptools in 2.5. (original) (raw)

Phillip J. Eby pje at telecommunity.com
Fri Apr 21 05:33:12 CEST 2006

At 11:08 PM 4/20/2006 -0400, Barry Warsaw wrote:

Question out of total ignorance: say I get a 3rd party package that has a standard distutils setup.py but knows nothing of setuptools. Say I install my own copy of setuptools (or have Python 2.5). Can that 3rd party package still be installed "the setuptools way" without modification?

Yes - that's what easy_install does, and that's a big part of what setuptools' monkeypatching is for. The 3rd party package thinks it's running with the distutils, but in fact it's running with setuptools. EasyInstall then just asks the package's setup.py to "bdist_egg", and once that's done, easy_install just dumps the egg into the installation location. Voila et fini.

My guess is that the original packager has to do /something/ to utilize setuptools (which is fine really -- I'm mostly just curious).

No. All they have to do is refrain from customizing the distutils beyond setuptools' ability to function. A package that thinks it's subclassing the distutils is actually subclassing setuptools, so if they change anything too fundamental, the whole house of cards comes down. For example, Twisted assigns distribution.extensions -- an attribute that's supposed to be a list of Extension objects or tuples -- to the number 1. This of course causes setuptools' brain to explode. :)

Their choice makes sense in distutils terms, because the distutils only checks for the truth of this attribute before it gets around to invoking the build_ext command -- which they replace. But setuptools does more complex things relating to extensions, because it needs to know how to build wrappers for them when they get put into eggs. So, this is a nice example of how complex it can be to extend the distutils in ways that don't break random popular packages.

Unfortunately, I can't yet fix this issue with Twisted, because setuptools doesn't yet support optional building of extensions. That's one piece of Marc's mxSetup framework that I've been looking to copy or steal once I get to really overhauling extension and library building. My OSAF work priorities put that work at a later time than now, however.

Anyway, that's a complete digression from the question you asked. As long as Mailman doesn't depend on building something like Numeric or Twisted, you can probably wrap it in easy_install. If it's not something that uses C code, you can just prebuild cross-platform eggs using easy_install. If it uses C code, you'd be able to build it on the target system.

I don't know what Python versions you support, though, and setuptools only goes back to Python 2.3. (Gotta give Google some incentive to upgrade.. ;) Although seriously it's because zipimport came in as of 2.3.)

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